Valsartan is an orally effective and specific angiotensin II (AT1) receptor antagonist, the chemical name of which is N-(1-valeryl)-N-[4-[2-(1H-tetrazolium-5-yl)phenyl]benzyl]-L-valine. Valsartan acts on AT1 receptor subtype selectively and blocks the combination of Ang II and AT1 receptor (the specific antagonism on AT1 receptor is about 30,000 times greater than that on AT2 receptor), to inhibit vasoconstriction and the release of aldosterone, achieving an antihypertensive effect.
During synthesis process, under the influence of the reaction conditions, a portion of valsartan products will be racemized to obtain D isomer of valsartan which is not pharmaceutically eligible. Valsartan comprising fewer isomers is obtained by crystallization in production. Meanwhile, the content of isomers in the mother liquor reaches more than or equal to 10%, even more than or equal to 20%, or yet even more than or equal to 30% (measured by HPLC area normalization method) after crystallization. Currently, no literature discloses a method excellent in recovering valsartan of pharmaceutically eligible configuration from the mother liquor with such a high content of isomers.
